Substrate structures applied in flexible electrical devices and fabrication method thereof

ABSTRACT

A substrate structure applied in flexible electrical devices is provided. The substrate structure includes a carrier, a release layer overlying the carrier with a first area and a flexible substrate overlying the release layer and the carrier with a second area, wherein the second area is larger than the first area and the flexible substrate has a greater adhesion force than that of the release layer to the carrier. The invention also provides a method for fabricating the substrate structure.

CROSS REFERENCE TO RELATED APPLICATIONS

This Application claims priority of Taiwan Patent Application No.97135351, filed on Sep. 15, 2008, the entirety of which is incorporatedby reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a substrate structure, and more particularly toa substrate structure applied in flexible electrical devices andfabrication method thereof.

2. Description of the Related Art

A flexible display is a development trend for new-generation displays,particularly an active flexible display. Compared to conventional heavyglass substrate with brittleness, development of light flexible plasticsubstrate is desirable, especially active full-color TFT display panel.Currently, fabrication techniques of active flexible display comprisea-Si TFT, LPTS TFT and OTFT. Display mediums comprise EPD, ECD, LCD andEL.

Fabrication processes are divided into batch type and roll to roll. ATFT apparatus can utilize batch type fabrication processes. However,development of substrate transfer and film separation techniques isrequired. The flexible display must be transferred to other plasticsubstrates from glass. For flexible displays using roll to rollfabrication processes, new apparatuses are required and some problemscaused by rolling and contact must be overcome.

The batch-type fabrication process has three methods. A PES substrate isbonded to a silicon wafer. A 7″ VGA (640×480) plastic LCD is obtained bya low-temperature a-Si TFT technique. In this manner, a transparentsubstrate material with heat-resistant, low thermal expansioncoefficient, low light hysteresis and chemical stability is required,and combined with proper gel materials and an advanced release technique(SEC Corporation). An LPTS TFT back cover is fabricated on glass. Theback cover is then removed from glass by laser annealing. The transfertechnique plays an important role for this method. In the transfertechnique, TFT devices with superior properties can be obtained due tono limitations by plastic substrates concerning fabrication temperatureso that conventional transparent plastic substrate can be utilized(Seiko Epson Corporation). Polyimide is coated on glass to develop ana-Si TFT-EPD display. The polyimide substrate is then taken off from theglass by the transfer technique. When the polyimide substrate isdirectly coated on glass, the fabrication temperature is permitted toachieve 300° C. and above due to heat-resistant thereof. However, usinglaser annealing to remove glass substrate is also required (PhilipsCorporation).

BRIEF SUMMARY OF THE INVENTION

One embodiment of the invention provides a substrate structure appliedin flexible electrical devices comprising a carrier, a release layeroverlying the carrier with a first area and a flexible substrateoverlying the release layer and the carrier with a second area, whereinthe second area is larger than the first area and the flexible substratehas a greater adhesion force than that of the release layer to thecarrier.

One embodiment of the invention provides a method for fabricating asubstrate structure applied in flexible electrical devices comprisingproviding a carrier, forming a release layer on the carrier with a firstarea and forming a flexible substrate on the release layer and thecarrier with a second area, wherein the second area is larger than thefirst area and the flexible substrate has a greater adhesion force thanthat of the release layer to the carrier.

The substrate structure applied in flexible electrical devices providedby the invention is simply fabricated using present semiconductorapparatuses, characterized by various adhesion forces of the two releaselayers to the carrier. A release layer with lower adhesion force isfirst formed on the carrier with a smaller area. Another release layerwith greater adhesion force (such as flexible display substrate) is thenformed on the release layer with lower adhesion force and contacts thecarrier with a larger area. According to the fabrication method, in TFTprocesses, the substrate structure is entirely, without peeling off. Therelease layer with greater adhesion force can be simply separated fromthe carrier by cutting along the two ends of the release layer withlower adhesion force.

A detailed description is given in the following embodiments withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be more fully understood by reading the subsequentdetailed description and examples with references made to theaccompanying drawing, wherein:

FIG. 1 is a cross-sectional view of a substrate structure applied inflexible electrical devices in an embodiment of the invention.

FIGS. 2A-2D are cross-sectional views of a method for fabricating asubstrate structure applied in flexible electrical devices in anembodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The following description is of the best-contemplated mode of carryingout the invention. This description is made for the purpose ofillustrating the general principles of the invention and should not betaken in a limiting sense. The scope of the invention is best determinedby reference to the appended claims.

In an embodiment, a substrate structure applied in flexible electricaldevices of the invention is shown in FIG. 1. The substrate structure 10comprises a carrier 12, a release layer 14 and a flexible substrate 16.The release layer 14 is formed on the carrier 12 with a first area A1.The flexible substrate 16 is formed on the release layer 14 and thecarrier 12 with a second area A2. Specifically, the second area A2 islarger than the first area A1 and the flexible substrate 16 has agreater adhesion force than that of the release layer 14 to the carrier12.

The carrier 12 may comprise glass or silicon wafer. The adhesion forceof the release layer 14 to the carrier 12 is 0B-1B.

The release layer 14 may comprise parylene or cyclic olefin copolymers(COC). The flexible substrate 16 may be a flexible display substrate,for example, an active flexible display substrate. The adhesion force ofthe flexible substrate 16 to the carrier 12 is 1-5B. The flexiblesubstrate 16 may comprise polyimide (PI), polycarbonate (PC),polyethersulfone (PES), polyacrylate (PA), polynorbornene (PNB),polyethylene terephthalate (PET), polyetheretherketone (PEEK),polyethylene naphthalate (PEN) or polyetherimide (PEI).

The polyimide (PI) flexible substrate 16 has formula (I):

In formula (I), A may comprise

wherein X and Y may comprise hydrogen, methyl, trifluoromethyl,hydroxyl, —OR, bromine, chlorine or iodine, and Z may comprise—O—,—CH2-, —C(CH3)2-, —SO2-, —Ar—O—Ar—, —Ar—CH2-Ar—, —Ar—C(CH3)2-Ar— or—Ar—SO2-Ar—, wherein R may comprise C1-18 alkyl, and Ar is benzene. Bmay comprise

wherein X and Y may comprise hydrogen, methyl, trifluoromethyl,hydroxyl, —OR, bromine, chlorine or iodine, and Z may comprise —O—,—CH2-, —C(CH3)2-, —SO2-, —Ar—O—Ar—, —Ar—CH2-Ar—, —Ar—C(CH3)2-Ar— or—Ar—SO2-Ar—, wherein R may comprise C1-18 alkyl, and Ar is benzene. nmay be an integer greater than 1.

The flexible substrate 16 may further comprise siloxane compounds orsilicon dioxide to increase its adhesion force to the carrier 12.

In an embodiment, a method for fabricating a substrate structure appliedin flexible electrical devices of the invention is shown in FIGS. 2A-2D.

Referring to FIG. 2A, a carrier 12 having a release layer 14 formedthereon with a first area A1 is provided. The release layer 14 is formedon the carrier 12 by, for example, coating or evaporation.

Next, referring to FIG. 2B, a flexible substrate 16 is formed on therelease layer 14 and the carrier 12 with a second area A2 by such ascoating. Specifically, the second area A2 is larger than the first areaA1 and the flexible substrate 16 has a greater adhesion force than thatof the release layer 14 to the carrier 12.

Next, referring to FIG. 2C, a portion of the flexible substrate 16 andthe carrier 12 is cut along two ends (C and C′) of the release layer 14to separate the release layer 14, the flexible substrate 16 and thecarrier 12, as shown in FIG. 2D.

The substrate structure applied in flexible electrical devices providedby the invention is simply fabricated using present semiconductorapparatuses, characterized by various adhesion forces of the two releaselayers to the carrier. A release layer with lower adhesion force isfirst formed on the carrier with a smaller area. Another release layerwith greater adhesion force (such as flexible display substrate) is thenformed on the release layer with lower adhesion force and contacts thecarrier with a larger area. According to the fabrication method, in TFTprocesses, the substrate structure is entirely, without peeling off. Therelease layer with greater adhesion force can be simply separated fromthe carrier by cutting along the two ends of the release layer withlower adhesion force.

A release layer is formed on a TFT glass (for example, 15 cm×15 cm). Thearea of the release layer is determined by a hollow pad (for example, 8cm×8 cm). A substrate is then formed on the glass with an area (forexample, 10 cm×10 cm) larger than that of the release layer to prepare asubstrate structure applied in flexible electrical devices. After devicefabrication is completed, a portion of the substrate and the releaselayer are cut along the two ends or the inside of the release layer toseparate the flexible electrical device from the glass.

EXAMPLE 1 Preparation of parylene Release Layer

A parylene precursor (parylene dimer) was put into a thermal evaporationapparatus. A clean glass (15 cm×15 cm) covered with a hollow pad (8 cm×8cm) was placed in a sample room. The parylene precursor was vaporized at150° C. and decomposed at 650° C. in a vacuum and then conducted intothe sample room. Parylene was deposited on the area uncovered by the padat room temperature. A parylene release layer (8 cm×8 cm) was prepared.

EXAMPLE 2 Preparation of Arton, Topas and Zeonor Release Layer

Arton, Topas and Zeonor (with 10% solid content dissolved in toluene)were coated on glasses using a scraper. The glass was baked in variousovens (80° C. and 150° C.) respectively for 0.5 hour. A release layer (8cm×8 cm) was prepared.

EXAMPLE 3 Preparation of polyimide (B1317-BAPPm, BB)/parylene/GlassSubstrate Structure

0.0147 mole diphenylamine (BAPPm) was completely dissolved in 32.94 gcresol under nitrogen at room temperature. 0.015 mole dianhydride(B1317) was then added and continuously stirred for 1 hour afterdianhydride (B1317) was completely dissolved to form a sticky polyamicacid (PAA) solution. Next, the PAA solution was thermally imidized (220°C.) for 3 hours, and water was simultaneously removed. Methanol wasfinally added to the resulting solution to precipitate polyimide andbaked in a vacuum oven for 12 hours. After baking, polyimide (with 20%solid content) was dissolved in DMAc to form a polyimide solution. Thepolyimide solution was then coated on the glass plated with 8 cm×8 cmparylene with an area (10 cm×10 cm) using a scraper. The glass was bakedin various ovens (80° C. and 150° C.) respectively for 1 hour. Apolyimide (BB)/parylene/glass substrate structure was prepared.

EXAMPLE 4 Preparation of silicon dioxide/polyimide(BB-37)/parylene/Glass Substrate Structure

3 g silicon dioxide (with 20% solid content dissolved in DMAc) and 7 gB1317-BAPPm (BB) (with 20% solid content dissolved in DMAc) were placedin a sample bottle. 0.3 g amino siloxane was then added to prepare asolution and stirred for 30 min under room temperature. Next, thesolution was coated on a glass plated with parylene using a scraper. Theglass was then baked in various ovens (80° C. and 150° C.) respectivelyfor 1 hour. A silicon dioxide/polyimide (BB-37)/parylene/glass substratestructure was prepared.

EXAMPLE 5 Preparation of silicon dioxide/polyimide(BB-55)/parylene/Glass Substrate Structure

5 g silicon dioxide (with 20% solid content dissolved in DMAc) and 5 gB1317-BAPPm (BB) (with 20% solid content dissolved in DMAc) were placedin a sample bottle. 0.2 g amino siloxane was then added to prepare asolution and stirred for 30 min under room temperature. Next, thesolution was coated on a glass plated with parylene using a scraper. Theglass was then baked in various ovens (80° C. and 150° C.) respectivelyfor 1 hour. A silicon dioxide/polyimide (BB-55)/parylene/glass substratestructure was prepared.

EXAMPLE 6 Preparation of silicon dioxide/polyimide(BB-73)/parylene/Glass Substrate Structure

7 g silicon dioxide (with 20% solid content dissolved in DMAc) and 3 gB1317-BAPPm (BB) (with 20% solid content dissolved in DMAc) were placedin a sample bottle. 0.12 g amino siloxane was then added to prepare asolution and stirred for 30 min under room temperature. Next, thesolution was coated on a glass plated with parylene using a scraper. Theglass was then baked in various ovens (80° C. and 150° C.) respectivelyfor 1 hour. A silicon dioxide/polyimide (BB-73)/parylene/glass substratestructure was prepared.

EXAMPLE 7 Preparation of tetraethoxysilane (TEOS)/polyimide(BB)/Topas/Glass Substrate Structure

0.2 g tetraethoxysilane (TEOS) and 10 g B1317-BAPPm (BB) (with 20% solidcontent dissolved in DMAc) were placed in a sample bottle to prepare asolution. Next, the solution was coated on a glass coated with Topasusing a scraper. The glass was then baked in various ovens (80° C. and150° C.) respectively for 1 hour. A tetraethoxysilane (TEOS)/polyimide(BB)/Topas/glass substrate structure was prepared.

EXAMPLE 8 Preparation of amino silane/polyimide (BB)/Zeonor/GlassSubstrate Structure

0.2 g amino silane and 10 g B1317-BAPPm (BB) (with 20% solid contentdissolved in DMAc) were placed in a sample bottle to prepare a solution.Next, the solution was coated on a glass coated with Zeonor using ascraper. The glass was then baked in various ovens (80° C. and 150° C.)respectively for 1 hour. An amino silane/polyimide (BB)/Zeonor/glasssubstrate structure was prepared.

EXAMPLE 9 Preparation of 3-(methacryloxy)propyl trimethoxy silane(MPMS)/polyimide (BB)/Arton/Glass Substrate Structure

0.2 g 3-(methacryloxy)propyl trimethoxy silane (MPMS) and 10 gB1317-BAPPm (BB) (with 20% solid content dissolved in DMAc) were placedin a sample bottle to prepare a solution. Next, the solution was coatedon a glass coated with Arton using a scraper. The glass was then bakedin various ovens (80° C. and 150° C.) respectively for 1 hour. A3-(methacryloxy)propyl trimethoxy silane (MPMS)/polyimide(BB)/Arton/glass substrate structure was prepared.

After the substrate structure was prepared, electrical devices werefabricated within the release layer. After device fabrication wascompleted, a portion of the substrate and the release layer were cutalong the two ends or the inside of the release layer to separate thesubstrate and the electrical device from the glass.

The adhesion force of the release layer and flexible substrate to thecarrier is shown in Table 1 and Table 2.

TABLE 1 Materials Adhesion force (B) Parylene (Example 1) 0 Topas(Example 2) 0 Zeonor (Example 2) 0 Arton (Example 2) 0 Polyimide(Example 3) 1 Polyimide/silicon dioxide 2-5 (Examples 4-6)Polyimide/TEOS 5 (Example 7) Polyimide/amino silane 5 (Example 8)Polyimide/MPMS 5 (Example 9)

TABLE 2 Silicon dioxide content (%) Adhesion force (B)  0 (Example 3) 130 (Example 4) 5 50 (Example 5) 3 70 (Example 6) 2

While the invention has been described by way of example and in terms ofpreferred embodiment, it is to be understood that the invention is notlimited thereto. To the contrary, it is intended to cover variousmodifications and similar arrangements (as would be apparent to thoseskilled in the art). Therefore, the scope of the appended claims shouldbe accorded the broadest interpretation so as to encompass all suchmodifications and similar arrangements.

1. A substrate structure applied in flexible electrical devices,comprising: a carrier; a release layer overlying the carrier with afirst area; and a flexible substrate overlying the release layer and thecarrier with a second area, wherein the second area is larger than thefirst area and the flexible substrate has a greater adhesion force thanthat of the release layer to the carrier.
 2. The substrate structureapplied in flexible electrical devices as claimed in claim 1, whereinthe carrier comprises glass or silicon wafer.
 3. The substrate structureapplied in flexible electrical devices as claimed in claim 1, whereinthe adhesion force of the release layer to the carrier is 0B-1B.
 4. Thesubstrate structure applied in flexible electrical devices as claimed inclaim 1, wherein the release layer comprises parylene or cyclic olefincopolymers (COC).
 5. The substrate structure applied in flexibleelectrical devices as claimed in claim 1, wherein the adhesion force ofthe flexible substrate to the carrier is 1-5B.
 6. The substratestructure applied in flexible electrical devices as claimed in claim 1,wherein the flexible substrate comprises polyimide (PI), polycarbonate(PC), polyethersulfone (PES), polyacrylate (PA), polynorbornene (PNB),polyethylene terephthalate (PET), polyetheretherketone (PEEK),polyethylene naphthalate (PEN) or polyetherimide (PEI).
 7. The substratestructure applied in flexible electrical devices as claimed in claim 6,wherein the polyimide (PI) has formula (I):

wherein A comprises

wherein X and Y comprise hydrogen, methyl, trifluoromethyl, hydroxyl,—OR, bromine, chlorine or iodine, and Z comprises —O—, —CH2-, —C(CH3)2-,—SO2-, —Ar—O—Ar—, —Ar—CH2-Ar—, —Ar—C(CH3)2-Ar— or —Ar—SO2-Ar—, wherein Rcomprises C1-18 alkyl, and Ar is benzene; B comprises

wherein X and Y comprise hydrogen, methyl, trifluoromethyl, hydroxyl,—OR, bromine, chlorine or iodine, and Z comprises —O—, —CH2-, —C(CH3)2-,—SO2-, —Ar—O—Ar—, —Ar—CH2-Ar—, —Ar—C(CH3)2-Ar— or —Ar—SO2-Ar—, wherein Rcomprises C1-18 alkyl, and Ar is benzene; and n is an integer greaterthan
 1. 8. The substrate structure applied in flexible electricaldevices as claimed in claim 6, wherein the flexible substrate furthercomprises siloxane compounds.
 9. The substrate structure applied inflexible electrical devices as claimed in claim 8, wherein the flexiblesubstrate further comprises silicon oxide.
 10. A method for fabricatinga substrate structure applied in flexible electrical devices,comprising: providing a carrier; forming a release layer on the carrierwith a first area; and forming a flexible substrate on the release layerand the carrier with a second area, wherein the second area is largerthan the first area and the flexible substrate has a greater adhesionforce than that of the release layer to the carrier.
 11. The method forfabricating a substrate structure applied in flexible electrical devicesas claimed in claim 10, wherein the release layer is formed on thecarrier by coating or evaporation.
 12. The method for fabricating asubstrate structure applied in flexible electrical devices as claimed inclaim 10, wherein the flexible substrate is formed on the release layerand the carrier by coating.
 13. The method for fabricating a substratestructure applied in flexible electrical devices as claimed in claim 10,further comprising cutting a portion of the flexible substrate and thecarrier along two ends or the inside of the release layer to separatethe release layer, the flexible substrate and the carrier.